Global food security depends on trade in just four crops: maize, wheat, rice and soybeans. The first three account for 60 percent of the world’s food energy intake. The fourth, soybeans, is the world’s largest source of animal protein feed, making up 65 percent of global protein feed supply. Their production is concentrated in a handful of exporting countries, including the United States, Brazil and the Black Sea region, from which they are flowing at ever-greater volumes. Between 2000 and 2015, global food trade grew by 127 percent to 2.2 billion metric tons — and growth rates are projected to keep increasing.

But the movement of these crops hinges on just 14 “choke-point” junctures on transport routes through which exceptional volumes of trade pass.

Such choke points have been perilously overlooked, said Rob Bailey, research director for energy, environment and resources at Chatham House and co-author of the report…

Brazil, the world’s other heavy-hitter, accounts for 17 percent of global wheat, maize, rice and soybean exports. But its road network is crumbling. Extreme rainfall could knock out a major transport route. If this happened together with a U.S. flood and a Russian drought, there would be global food shortages, riots and political instability, starvation in areas that are heavily dependent on imports, and recessions everywhere else…

Disruption at any of these choke points would mean trouble, but if several jammed at once, it could be disastrous.

Climate change makes such a scenario more likely. While it’s difficult to connect any specific weather event to climate change, models suggest the shifting climate is making such events more common.

For the United States, the could mean a lot more episodes like the one in August 2012, when Hurricane Isaac closed ports and suspended barge traffic on parts of the Mississippi River…

Political instability can also cause choke point disruptions. In 2015 and 2016, tensions between Russia and Turkey fueled power plays in the Turkish Straits, and an attempted internal coup led to a temporary shutdown of the Bosporus.

And disruption of key arteries due to political instability can lead to a self-reinforcing cycle, as food shortages breed further instability. In the Middle East and North Africa, statistical analyses show that food security is a particularly high indicator of political stability. Over a third of grain imports for the region pass through a maritime choke point for which there is no alternate route. But the problem is widespread. The 2007-2008 global food crisis was accompanied by protests in 61 countries and riots in 23…

To make matters worse, chronic underinvestment in infrastructure has weakened critical networks. Extreme weather and increased trade flows put them at risk of failing. The McKinsey Global Institute places the world’s infrastructure investment deficit — the gap between funding available and funding needed — at $250 billion a year through 2040. (The United States has one of the largest deficits among G-20 countries, according to Chatham House.) But even where there is infrastructure investment, governments often fail to factor in climate risks: A 2016 survey by the Organization for Economic Cooperation and Development found that, with very few exceptions, they are largely overlooked even in rich countries.

“It is a glide path to a perfect storm,” said Bailey.

In fact, 13 of the 14 choke points have seen some form of temporary disruption or closure in the last 15 years, according to the report. (The only one that hasn’t, the Strait of Gibraltar, may now come under pressure in Brexit negotiations.) This should prompt policymakers to prepare for worst-case scenarios. But as Bailey observed, “We’re not very good at conceptualizing risks which we haven’t yet experienced.” The mentality is very different when it comes to the oil market, where past oil embargoes make the idea of a supply shock more tangible. “People obsess about choke points there,” he said…

“What is needed is a coordinated international approach like you have in energy markets,” Bailey said. In 1974, the International Energy Agency established emergency response mechanisms to minimize the risk of oil and gas disruptions. Governments and international responders, like the Food and Agriculture Organization of the United Nations and the U.N. World Food Program, should model this with rules on coordination during acute food disruptions. This would include emergency food supply sharing arrangements and smarter strategic storage — where choke points can’t cut off supply.

But they also needed to take preventive measures, like diversifying production so countries aren’t dependent on a handful of mega-crops and exporters. Funding should support alternative sources and supply routes around the world, as well as climate-resilient infrastructure. But all of this requires long-term planning. It needs to start now — before extreme weather becomes even more frequent.